Oil and Gas Terms Beginning with “R” — Page 3

A cementslurry made with less mix water than is customarily used without modifying additives. Read more →

A cementslurry made with less mix water than is customarily used without modifying additives. Read more →

A reducing agent in oilfield acid stimulation chemistry is a chemical additive added to the acid system to stabilize iron in solution and prevent precipitation of insoluble iron compounds that would damage the formation… Read more →

A reef in petroleum geology is a biologically constructed carbonate rock body — built by corals, stromatoporoids, algae, sponges, rudists, or microbial communities — that forms a discrete, typically mound-shaped or… Read more →

A reel in coiled tubing operations is the specialized device used to store and transport a continuous coiled tubing string in a wound configuration, ready for deployment at the wellsite for various intervention… Read more →

Reel back-tension is the controlled pulling force a coiled tubing (CT) reel maintains against the injector head as the continuous string spools on or off the drum during a well intervention. The reel drive, usually a… Read more →

A reference point is the specific physical position on a wireline logging tool string or measurement-while-drilling (MWD/LWD) tool assembly that is designated as the depth datum from which all formation measurements in… Read more →

What Is Reflection in Seismic Exploration? In oil and gas seismic exploration, a reflection is the return of a portion of an acoustic or elastic wave's energy back toward the surface when the wave encounters a boundary… Read more →

The reflection coefficient in seismic exploration is a dimensionless quantity (ranging from -1 to +1) that describes what fraction of an incident seismic wave's amplitude is reflected at an interface between two… Read more →

Reflection tomography is a seismic velocity analysis technique that uses the travel times of reflected seismic waves recorded at multiple offsets (source-receiver distances) to iteratively update a subsurface velocity… Read more →

A reflector in seismic exploration is a subsurface interface between geological layers with contrasting acoustic impedances (the product of rock density and seismic wave velocity) that reflects a portion of an incident… Read more →

Refraction in geophysics is the change in direction of propagation of a seismic or electromagnetic wave as it passes from one medium (rock layer or fluid) into another medium with a different wave velocity, governed by… Read more →

The refractive index is a number that tells you how much a particular material slows down light compared to a vacuum. The symbol is the letter n. Vacuum has a refractive index of exactly 1. Air is essentially 1. Water… Read more →

A refractor in seismic exploration is a subsurface layer of rock with sufficient thickness, lateral extent, and significantly higher acoustic velocity than the rocks immediately above it that it can transmit a head wave… Read more →

Refracturing (also written re-fracturing) is the process of hydraulically fracturing a previously hydraulically fractured well a second or subsequent time, typically years after the initial completion, with the… Read more →

In oil and gas applications, regression has two distinct meanings. In statistics and data analysis, regression is the mathematical process of fitting a trend line or curve to a set of data points, producing an equation… Read more →

The regression coefficient, most commonly reported as the coefficient of determination R² (or as the correlation coefficient r in linear contexts), is a dimensionless statistic that quantifies how well a fitted curve or… Read more →

Relative age is the age of a rock unit, formation, or geological event expressed as older or younger than another feature by applying stratigraphic principles, biostratigraphy, lithostratigraphy, chemostratigraphy, and… Read more →

The relative dielectric permittivity (also called relative dielectric constant or relative permittivity) of a material is the dimensionless ratio of the absolute dielectric permittivity epsilon (the degree to which the… Read more →

Relative filtrate volume is the ratio of the drilling fluid filtrate volume measured under a standard test to the filtrate volume from a reference formulation tested under identical conditions, providing a normalized… Read more →

Relative humidity in the context of oil-based and synthetic-based drilling fluids is the water activity of the fluid's internal aqueous phase — expressed as the ratio of the water vapor pressure of the brine phase… Read more →

What Is Relative Permeability? Relative permeability (kr) is the ratio of effective permeability of a phase (oil, water, or gas) in a multiphase system to the absolute permeability of the rock at 100% saturation of that… Read more →

Relaxation time in nuclear magnetic resonance (NMR) well logging refers to the characteristic time constants — T1 (longitudinal or spin-lattice relaxation time) and T2 (transverse or spin-spin relaxation time) — that… Read more →

A release joint is a downhole tool engineered to part along a single, predetermined plane under controlled conditions, allowing an operator to separate the upper portion of a tool string and retrieve it to surface while… Read more →

Relinquishment is the return of part or all of an oil and gas lease, licence, or concession to the party that granted it, whether a private lessor, a farmor in a farmout deal, or a host government acting as resource… Read more →

Remedial cementing covers any cementing operation performed after the original (primary) cementing of a well, to fix problems with the original cement job or to address conditions that develop later. The most common… Read more →

Remote sensing in the petroleum industry refers to the acquisition and analysis of data about the Earth's surface and subsurface from a distance — using sensors mounted on satellites, aircraft, drones, or ground… Read more →

A remotely operated vehicle (ROV) in oil and gas operations is an unoccupied, tethered underwater robot operated from a surface vessel or platform by pilots using real-time video feeds and sensor data transmitted… Read more →

A repeat section in wireline logging is a short logging pass (typically 30 to 100 meters long) that re-runs the same tool string over a previously logged interval to verify the repeatability and accuracy of the log… Read more →

Repeatability in oilfield measurement and testing refers to the degree to which the same measurement procedure applied to the same sample or formation under the same conditions by the same operator using the same… Read more →